Blend of flame-retardant poly (ethylene-2,6-napthalene dicarboxylate) fibers and flame-retardant cellulosic fibers

ABSTRACT

Flame-retardant yarns and fabrics of a combination of (1) fibers of poly(ethylene-2,6-naphthalene dicarboxylate) resin containing a flame-retardant amount of a specified aryl spirophosphate and (2) flame-retardant cellulosic fibers.

United States Patent 1191 Knopka 1 1 Feb. 18, 1975 1 BLEND OF FLAME-RETARDANT POLY (ETHYLENE-2,6-NAPTHALENE DICARBOXYLATE) FIBERS AND FLAME-RETARDANT CELLULOSIC FIBERS [75] Inventor: William N. Knopka, Wilmington,

Del.

] Assignee: FMC Corporation, Philadelpia, Pa.

] Filed: July 18, 1973 Appl. N0.: 380,345

[52} US. Cl 57/140 BY, 260/9, 260/47 R, 260/75 R, 260/75 H [51] Int. Cl D02g 3/04 [58} Field of Search ..57/14O R, 140 BY, 140 C, 57/153,157 R;260/9, 16, 47 R, 47 C, 75 R,

75 H, 75 S, 45.75 R, 45.9 R, 860, 49

[56] References Cited UNITED STATES PATENTS 3.110,547 11/1963 Emmert 260/75 H Primary Examiner l0hn Petrakes [57] ABSTRACT Flame-retardant yarns and fabrics of a combination of (1) fibers of po1y(ethylene-2.6-naphtha1ene dicarboxylate) resin containing a flame-retardant amount of a specified aryl spirophosphate and (2) flameretardant cellulosic fibers.

10 Claims, N0 Drawings BLEND OF FLAME-RETARDANT POLY (ETHYLENE-2,6-NAPTHALENE DICARBOXYLATE) FIBERS AND FLAME-RETARDANT CELLULOSIC FIBERS The most commercially important polyester textile fibers have been those prepared from polyethylene terephthalate resins. Because of their commercial importance and the great concern for flame-retardant textile fabrics, attempts have been made to provide flameretardant properties for these flammable polyester materials. One of the methods used required the physical incorporation of flame-retardant chemicals in the polymer composition. However, in the case of textile fibers, the high amounts of flame-retardant chemicals necessary to impart the degree of flame-retardancy required by stringent federal regulations embrittles the fibers and detrimentally affects the physical properties thereof.

The need for a polyester fiber which has good physical properties and high flame-retardancy is most critical for yarn and fabric blends of polyester fibers and cellulosic fibers. Polyester-cellulosic fiber blends pro vide textile fabrics having the highly desirable wear characteristics of polyester fabrics with highly desirable comfort characteristics of cellulosic fabrics. Polyester fibers are thermoplastic and when exposed to a flame, burn and melt away from the flame, thus extinguishing themselves. If polyester fibers are blended with flammable cellulosic fibers and exposed to a flame, the polyester is more likely to continue burning even when melting since the burning cellulose fiber continuously ignites it. If polyester fibers are blended with flameretardant cellulosic fibers and the blend ignited, the flame-retardant cellulosic fibers burn only in the area of flame contact. However, the flame-retardant cellulosic fiber prevents the polyester fiber from shrinking and dripping away from the flame and the polyester continues to burn.

It is a primary object of this invention to provide more useful flame-retardant yarns and fabrics of blends or combinations of polyester fibers and cellulosic fibers.

It is another object of this invention to provide yarns and fabrics of good physical properties from blends of flame-retardant polyester fibers and flame-retardant cellulosic fibers which yarns and fabrics will meet more stringent flame-retardant requirements.

Polyesters as employed herein have reference to F1- ber-forming polymers ofglycols and dicarboxylic acids, hydroxycarboxylic acids, and combinations thereof.

These and other objects are attained in accordance with this invention which comprises flame-retardant yarns and fabrics of a combination of (l) fibers of a polyester resin of at least 75 mol percent of ethylene- 2,6-naphthalene dicarboxylate units and up to 25 mol percent of other ester units, and an aryl spirophosphate of the general formula wherein R, and R represent aryl radicals selected from the group consisting of phenyl, naphthyl, phenyl and naphthyl radicals containing 1 to 3 chlorine or bromine atoms and further substituted derivatives thereof the substituents being selected from the group consisting of lower alkyl, lower alkoxy, phenyl, phenoxy. and phenyl or phenoxy containing 1 to 5 chlorine or bromine atoms, said spirophosphate being mixed with said polyester resin in an amount sufficient to increase the flame-retardancy thereof, and (2) flame-retardant cellulosic fibers. The aforesaid spirophosphates not only impart a high degree of flameaetardancy to polyesters. but, importantly, they are compatible with and soluble in molten polyesters and are thereby easily incorpo rated therein. Moreover, they are thermally stable at the elevated temperatures, i.e., about 250-350C. encountered in carrying out extrusion or melt spinning processes, have a low volatility at these high temperatures, have no adverse effect upon the physical properties of the polyester, exhibit hydrolytic stability and are non-toxic.

R, and R of the formula set forth above may be plienyl and naphthyl radicals, and phenyl and naphthyl radicals each containing from 1 to 3 chlorine or bromine atoms. These phenyl, naphthyl or mono-, dior trihalogenated phenyl or naphthyl radicals, the halogen being chlorine or bromine, may contain further substituents selected from the group consisting of lower alkyl or alkoxy of l to 3 carbon atoms each, phenyl, phenoxy and chlorinated or brominated phenyl or phenoxy and there may be 1 to 5 chlorine or bromine atoms present in the phenyl or phenoxy substituents which are linked through a C-C- or a C-O bond to the R, or R aryl group. It has been found that the R, or R aryl radicals cannot be completely brominated or chlorinated, since a loss of stability may occur, but on the other hand, a phenyl or phenoxy substituent attached to an R, or R aryl can be completely chlorinated or brominated with no adverse effects.

The spirophosphates are generally and preferably symmetrical, but if desired, asymmetrical compounds may be prepared in accordance with known techniques.

Particularly preferred are those aryl spirophosphates of the above formula wherein R, and R represent phenyl, naphthyl, mono-, or di-bromophenyl, and mono-. dior tribromonaphthyl. Preferred embodiments of this group are those spirophosphates wherein R, and R represent l-bromo-Z-naphthyl, l,6-dibromo-2- naphthyl and l,3,6-tribromo-2-naphthyl.

Suitable processes for preparing spirophosphates are disclosed, for example, in US. Pat. No. 3,090,799, issued May 21, 1963, to Wahl et al. Thus, (a) pentaerythritol is reacted with a suitable aryl ester of phosphorus oxychloride, or (b) a pentaerythritol ester of phosphorochloridic acid, a spiro compound, is reacted with an aryl compound of the formula ROH or the alkali-metal salt thereof, the R representing the desired aryl radicals. Other suitable methods of preparation are readily apparent to those skilled in the art.

Generally speaking, from about 5 to 25 percent of the flame-retardant aryl spirophosphate is employed based on the combined weight of polyester and additive, i.e., 5 to 25 parts by weight of flame-retardant and 95 to parts of polyester. The addition of amounts substantially in excess of about 25 percent may interfere with the physical properties of the finished fiber as well as with the proper operation of processing equipment, particularly the spinnerets used in making polyester fibers. The exact amount of flame-retardant required will depend upon its phosphorus content and. if

present, its chlorine or bromine content, as well as on the degree of flame-retardancy desired. Generally, for a flame-retardant aryl spirophosphate containing only phosphorus, the amount used is that necessary to incorporate about 0.5 to 3.0 percent by weight phosphorus based on the total weight of polyester and flameretardant. When chlorine or bromine is present in the aryl spirophosphate compound, particularly bromine, the desirable phosphorus content is between about 0.3 to 2.5 percent by weight and the desirable chlorine or bromine content is between about I to 10 percent by weight. In many cases with chlorine or bromine, a synergistic effect is noted with phosphorus. Such an effect can lower the desirable phosphorus content to 0.1 to 1.5 percent by weight based on the combined weight of polyester and spirophosphate.

In addition to the aryl spirophosphate, various flameretardant organic bromine or chlorine compounds which contain at least 40 wt. percent of the halogen can be physically incorporated in the polyester resin in amounts sufficient to provide from at least 5 up to about 25 percent halogen, more preferably from about l0 to about 20 percent, based on the weight of the polyester resin.

Examples of halogen compounds useful for this invcntion are included in the following formula wherein X is chlorine or bromine, Y is R, OR, or -OROR, where R is an alkyl radical having from I to carbon atoms, and aryl radical having from 6 to 24 atoms, an aralkyl radical having from 6 to 16 atoms and the halides thereof, R is an alkylene radical having from I to 6 carbon atoms, n and m are positive integers satisfying the expression 6 m l, 5 n 0.

Examples of halogen compounds useful for this invention include polybrominated diphenyls, polybrominated diphenyl ethers, polybrominated diphenyl carbonates, tetrabromophthalic anhydride, tetrabromophthalic-imide, tetrabromobisphenol A difatty acid ester. tetrabromobisphenol S di-fatty acid ester, hexabromobenzene, polybrominated poly(pentaerythritol) (see U.S. Pat. No. 3,700,625), polybrominated carbonates containing neopentyl groups (see U.S. Pat. No. 3,688,001), brominated polyethers (see U.S. Pat. No. 3,645,962), polybrominated terphenyls, polybrominated anthracenes, pentabromo toluene, pentabromo benzyl bromide, polybrominated diphenoxyalkanes, tetrabromobisphenol A dimethyl ether (see U.S. Pat. No. 3,658,634). The bromine radicals are replaced with chlorine radicals to provide corresponding chlorine containing compounds.

These compounds are used alone or in combination to supply the required amount of halogen for the composition. Preferably, the compounds contain at least 60 percent by weight of bromine or chlorine in order to permit the incorporation of less of the organic halogenated compound in the polyester resin composition for optimum flame-retardancy and physical properties.

Small amounts of metal compounds, e.g., antimony trioxide, zinc oxide or alumina, are advantageously employed with the organic halogen compounds to provide additional flame-retardancy.

While fibers prepared from ethylene-2,6- naphthalene dicarboxylate homopolymer resin are preferred for this invention, up to 25 mol percent of other ester units are randomly placed in the polyester chain with ethylene-2,6-naphthalene dicarboxylate units to obtain thermoplastic resins for fibers having improved or varied characteristics. The other ester units are usually derived from other diacids and diols and include, for example, terephthalic acid, bibenzoic acid, sodium sulfoisophthalic acid, diphenoxyalkane dicarboxylic acids, malonic acid, glutaric acid, and the like; hydroxyalkoxybenzoic acids, adipic acid, and alkylene glycols having from 3 to 12 carbon atoms, gem-dialkyl glycols, bis (hydroxymethyl)cyclohexane, diethylene gylcol and the like. glycol The diacids and/or diols can be halogenated to provide additional flame-retardant properties for the resin. Where halogenated, i.e., brominated or chlorinated, diacids or diols are employed, they may be described as being present in the copolyester chain halogenated ester. units each having the following general formula o-G 0-li 1t cwhere G is the residue ofa diol or functional equivalent thereof, A is the residue of a dicarboxylic acid or functional equivalent thereof and either G, A or both are substituted with one or more halogen atoms including either bromine, chlorine or both. The functional equivalents of the diol include, for example, epoxides or lower acid esters, e.g., acetic acid esters, and the functional equivalents of the dicarboxylic acid include, for example, carbonyl halides, anhydrides, salts and esters of lower alcohols. These functional equivalents for diols and dicarboxylic acids and their reactivity in forming ester units, as generally described above, are well known and need not be described in further detail.

At least one of the radicals G and A are multivalent organic radicals depending principally on the number of halogen atoms attached thereto. These radicals are preferably hydrocarbon and more preferably aromatic hydrocarbon radicals but generally include aliphatic, substituted aliphatic, cycloaliphatic including heterocyclic radicals, aromatic and substituted aromatic radicals. These radicals may have various atoms, other than carbon, as an integral link in the radical chain or as substituents including, for example, chalcogens, nitrogen and phosphorus. In addition, various substituent and linking groups may be present in the organic radical including, for example, sulfonic acid groups, sulfinic acid groups, phosphonic acid groups, phosphinic acid groups, salts of these acid groups, imide groups, amide groups, amine groups and the like.

In one of the preferred aspects of this invention, the diol portion of the halogenated ester unit is derived from a non-halogenated alkylene glycol of the general formula HOCH ,,Ol-I wherein n is an integer of 2 to 10, and the dicarboxylic acid portion contains a halogenated phenylene or halogenated naphthalene base radical. In another preferred aspect of this invention, the diol portion of the halogenated ester unit is derived from a diol having the fol.- lowing general formula wherein R and R are the same or different radicals in cluding hydrogen, an alkyl radical having from 1 to 6 carbon atoms or an aromatic radical, and n is zero or one; and the dicarboxylic acid portion contains a halogenated or non-halogenated phenylene or naphthalene base radical.

There are various known methods for the preparation of filament-forming polyester resins, Of these, the two most commonly employed are the so-called transesterification method and the direct esterification method. In the former, a lower alkanol diester is reacted with a diol and the product polycondensed while in the latter, the diacid is reacted directly with a diol and the product polycondensed. Any method for preparing high molecular weight poly(ethylene-2,6- naphthalene dicarboxylate) is suitable for this invention.

The polyester and copolyester resins used for this invention are those having an intrinsic viscosity of at least 0.2 and'preferably 0.4 (determined in a 60 weight percent phenol and 40 weight percent tetrachloroethane solution) at 30C.

The polyester resin of the fiber blend of this invention can have incorporated therein various additives for improving the resin properties including, for example, heat and ultra-violet light stabilizers, antioxidants, antistatic agents, plasticizers, dyes, pigments and the like along with the flame-retardant.

The physical mixture of polyester resin and flameretardant material is conventionally prepared by mixing the resin and the spirophosphate to obtain a substantially homogeneous product. The constituents can be premixed by tumbling, rolling or other mixing means and when fibers are produced by melt extrusion, a more homogeneous mass results during the processing. Alternatively, the spirophosphate in molten form can be injected into the polyester melt prior to spinning into fibers.

Polyester fibers or filaments are usually formed by melt extrusion of the resin composition through a multihole spinneret in a conventional manner. The as-spun yarn is then conventionally oriented to produce textile yarn of the continuous filament or staple fiber type.

Flame-retardant cellulosic fibers preferably include cotton, rayon or cellulose acetate fibers which have been combined, impregnated or coated with flameretardant chemicals which provide substantially permanent flame-retardant properties therefor without degrading the physical properties of the fiber. That is, the

cellulosic fibers or fabrics produced therefrom should be capable of withstanding periodic washing or cleaning with conventional dry cleaning solvents without losing much of their flame'retardant properties. Many flame-retardant treatments for cellulosic fibers are known and several have been found to produce substantially permanent flame-retardancy. It is preferred, in the case of artificially prepared cellulosic fibers such as rayon and cellulose acetate, that the flame-retardant chemical be incorporated into the cellulosic spinning solution thereby providing cellulosic fibers having the flame-retardant locked in the cellulosic matrix. Examples of the preparation of these types of cellulosic fibers are found in U.S. Pat. Nos. 2,816,004. 3,266,918, 3,321,330, 3,455,713, 3,645,936 and 3,704,144.

One preferred form of this invention involves the use of the flame-retardant regenerated cellulose filaments or fibers described in US. Pat. No. 3,455,713. These fibers have been found to have excellent physical properties and permanent flame-retardancy. In brief, they are regenerated cellulose filaments having dispersed therein a substantially water-insoluble, liquid phosphonitrilate polymer having the general formula wherein R and R are the same of different alkyl or alkenyl radicals having from 1 to 6 carbon atoms and n is an integer of at least 3.

These filaments are preferably prepared by incorporating a flame-retarding amount of the phosphonitrilate polymer in filament-forming viscose, and spinning and regenerating filaments.

In another aspect of the invention, the flameretardant cellulosic fibers are cellulose acetate fibers prepared by incorporating compounds such as tris- (2,3 dibromopropyl)phosphate or similar compounds as disclosed in US. Pat. No. 3,321,330 into the acetate spinning dope and wet or dry spinning the fibers.

The blended or combined flame-retardant polyester and cellulosic fibers are used in various fiber and fabric constructions including, for example, spun staple yarns, mixed or tangled continuous filament yarns, novelty yarns, knit, woven and non-woven fabrics.

The flame-retardant polyester fibers and cellulose fibers described herein can also be blended with or combined in a fabric with normally flame-retardant fibers including, for example, glass fibers, polyvinyl chloride fibers, asbestos fibers, metal fibers, modacrylic fibers such as available under the trademark Dynel and Verel, and aromatic ring polyamide fibers such as available under the trademark Nomex. The yarn or fabrics of this invention will generally contain from about 10 to about 90, preferably about 20 to about weight percent of the flame-retardant polyester fibers and about to about 10, preferably about 80 to about 20 weight percent of the flame-retardant cellulosic fibers.

The following examples are set forth to demonstrate this invention.

EXAMPLE I A flame-retardant spirophosphate having the formula is prepared as follows: A 12 liter, three-neck flask was charged with 272 g. pentaerythritol (2.0 mole), 5,400 ml methylene chloride, and 640 g. of pyridine. The mixture was stirred and cooled to 12 in an ice water bath. A mixture of 844 g. (4mo1es) of phenyl dichlorophosphate and 540 ml of methylene chloride was added in 1.25 hours at 12-15. The mixture was stirred a few minutes and the ice water bath was lowered. An exotherm developed gradually raising the temperature to 38-40C. The ice bath was raised and cooling provided to maintain a gentle reflux. After the exotherm, the reaction mixture was refluxed for three hours and let stand overnight.

The mixture was filtered collecting 987 g. pyridine hydrochloride which contained 66.1 g of product. The filtrate was distilled collecting 4,500 ml of solvent. The residue was cooled, combined with the residue ofa parallel run and allowed to stand overnight.

Filtration, washing and drying gave 2,200 g. of a mixture of product and pyridine hydrochloride. The solids were stirred with 3 liters of distilled water and filtered. The process was repeated twice until the filtrate showed no presence of chloride. After drying 18 hours at 1 mm and 65, 1,080 g. was obtained (65.5 percent yield), m.p. 195.5 197.5.

The methylene chloride filtrate was condensed to 1,400 ml. After filtration, water washing and drying, 150 g. of good product was obtained, m.p. 195.5 198. Total yield 1,230 g. (74.6 percent).

Further concentration of the methylene chloride filtrate gave 31.8 g., m.p. 194.5-196.

Elemental Analyses:

Calculated for C H O P z %C, 49.54; H, 4.40; P,

Found: %C, 49.54; H, 4.21; P, 15.27.

Various spirophosphate derivatives, as defined for this invention, were prepared by reacting a substituted To provide control yarns and fabrics for comparison with the yarns of this invention, the following procedure was carried out.

Physical blends of a filament-forming polyethylene terephthalate resin and the aryl spirophosphate of Example 1 were melt spun from a laboratory spinning apparatus into yarns having 10 filaments. The yarns were conventionally drawn and plied with flame-retardant rayon yarn having a denier/filament of 1.5. The yarn blends were knitted into sleeves on a Lawson knitting machine.

The flame-retardant rayon yarn was prepared by incorporating water-insoluble. liquid polymers of di-npropyl phosphonitrilate in viscose and thereafter spinning the viscose into a coagulating and regenerating bath as described in US Pat. No. 3,455,713 to Godfrey. This provided a rayon yarn wherein each filament contained about 15 percent by weight of the phosphonitrilate dispersed therein.

The characteristics and properties of three different yarn blends in fabric form prepared as described above are set forth in the following table:

Table 11 Fabric Phosphorous,* Yarn Denier Blend 1 Fabric wt. No. 7: Polyester Rayon Polyester/Rayon o7../yd.'-

* phosphorous found in polyester fabric.

the formula The R substituent for various compounds prepared is given in the following table with the melting point of the spirophosphate compound.

Each of the knitted fabrics characterized in Table 11 were tested for flammability using the vertical flammability testing apparatus and procedure as defined by the US. Department of Commerce Standard FF-3-71 (37 PR. 146, 424), Standard for the Flammability ofChildrens Sleepwear. The fabric is considered flameretardant if the average char length of five samples does not exceed seven inches, no individual sample has a char length of 10 inches and no sample has a residual flame time (after flame) greater than 10 seconds. Less than five samples may be used if the first samples demonstrate that the fabric will not pass the test.

The results of the tests on each of the fabrics charac- T bl V terized in Table II are set forth in the following table:

Fabric No. I

T bl [[1 5 Sample 3 second test bone dry No. After Flame Char Length 1 37 sec. I inches Fabric Na 1 2 35 do. 10 do. 3 Second s: 3 36 (l0. 10 do. 4 42 do. 10 do. Sample No. After Flame Char Length 0 5 35 1 2 sec. 2.38 inches Fabric 2 2 51 l sec. 7.69 inches 2 NAF 1.50 do. 3 3 NAF 1.75 do. 4 2.0 sec. 3.88 do. 1 48 l0 5 5 (No more fabric available) 2 48 do. I0 do. 3 I do. 3 do. Fabric No. 3

Filhrlc N 3 4 sec. 2.06 inches 2 5 do. 2.50 do. 1 98 sec. l0 do. 7 3 3 do. 2.75 do. 1 71 do. 10 do. J) 4 4 do. 331 do. 3 ill do. it) do. 5 3 do. 1.50 do. 4 87 do. lf) do. 5 4 d0. 2.94 do. 5 ox do. 10 do. abric No. 4

-l'es1 conducted on hone dry samples. l 23 580 l0 iIlClIs- 25 Z I do. 3.38 do. 3 NAF 3.25 do.

It can be seen lrom the above data that the described 4 NAF 2.63 do. fabrics prepared from polyethylene terephthalate resin 5 NAF yarns containing varying amounts of the aryl spirophos- MP an flame phate blended with flame-retardant rayon yarns do not pass the Commerce Department Flammability Test with the amounts of additive employed It can be seen from the foregoing tabulated data that the described fabrics prepared from poly(ethylene-2.6-

naphthalene dicarboxylate) resin yarns containing EXAMPLE "I varying amounts of the aryl spirophosphate blended with flame-retardant rayon yarns much more readily "f fabncspf thls mvemlon P P pass the Commerce Department Flammability Test. No melt spmnmg p y blends a filamem'formlrlg flaming drips from the samples during these tests were P M -gv p dlcarboxylate) r651" observed. The fabric prepared with the polyester yarn and the ry P P P 0f EXflmPle I from a labO- containing 0.98 percent phosphorus failed the test but mtory spmmng apparatus Y havmg 10 flla- 40 those prepared with polyester fibers containing 1.36 ments. The yarns were conventionally drawn and plied d 195 percent phosphorous h d q lified pass with flame-retardant rayon yarn as descnbed for Examsuits, The fabric prepared from the polyester yarn conple II. The yarn blends were knitted into sleeves on a taining 2.35 percent phosphorous passed the test with- Lawson knitting machine. out qualification.

The characteristics and properties of four different These results when compared to those of Example ll yarn blends in fabric form prepared as described above are believed to be quite unexpected when taking the are set forth in the following table. stringent test requirements into consideration.

Table IV Fabric Phosphorous* Yarn Denier Blend 7: Fabric Weight No. 77 Polyester Rayon Polyester/Rayon oz./yd.

-Z Phosphorous found in polyester Each of the knitted fabrics characterized in Table ll Furthermore, it is known that the incorporation of was tested for flammability using the vertical flammavarious additives in polyester resins tend to degrade the bility test as defined by the US. Department of Comexcellent fiber properties thereof. If it is necessary to merce Standard FF 3-71 as described for Example ll. incorporate more flame-retardant additive in the poly The results of the tests on each of the fabrics are set ester resin to provide the desired flame-retardancy, as f h i h f ll i bl would be the case of poly(ethylene terephthalate) resin, this additional additive amount will make fibers prepared from the resin physically weaker and asa result these fibers will not provide the wear or wash-wear performance typical of the polyester-cellulosic fabric. The polyester-cellulosic fiber blend of this invention provides fabrics of high flame-retardancy without unacceptable loss of excellent fiber properties.

In a like manner, as described in Example "I, the additional spirophosphate derivatives as listed in Example I will provide good flame-retardancy for poly(ethylene- 2,6-naphthalene dicarboxylate) resin fibers used in combination with flame-retardant cellulosic fibers for the preparation of textile fabrics such that blended yarns of these fibers will have excellent flame-retardant and physical properties.

Various changes and modifications may be made in practicing the invention without departing from the spirit and scope thereof and, therefore, the invention is not to be limited except as defined in the appended claims.

l claim:

1. Flame-retardant yarns and fabrics of a combination of (l) fibers of a saturated polyester resin of at least 75 mol percent ethylene-2,6-naphthalene dicarboxylate units and up to 25 spirophosphate mol percent of other ester units and an aryl spitophosphate of the formula Rlo OCH:/ \CH2-C R2 wherein R and R represent aryl radicals selected from the group consisting of phenyl, naphthyl, phenyl and naphthyl radicals containing 1 to 3 chlorine or bromine atoms, and further substituted derivatives thereof the substituents being selected from the group consisting of lower alkyl, lower alkoxy, phenyl, phenoxy and phenyl or phenoxy radicals containing from 1 to 5 chlorine or bromine atoms, said spirophosphate being mixed with said polyester resin in an amount sufficient to increase the flame-retardancy thereof; and (2) flame-retardant cellulosic fibers, the polyester fibers being present in an amount of from about to 90 weight percent and the cellulosic fibers being present in an amount of from about 90 to 10 weight percent.

2. The flame-retardant yarns and fabrics of claim 1 wherein R, and R are both phenyl radicals and the spirophosphate is mixed with the polyester resin in an amount ranging from about 5 to about 25 percent, based on the combined weight of the polyester resin and spirophosphate.

3. The flame-retardant yarns and fabrics of claim 1 wherein R and R are both mono-, dior tri-bromosubstituted phenyl radicals.

4. The flame-retardant yarns and fabrics of claim 1 wherein the polyester resin is the homopolymer of ethylene-2,6-naphthalene dicarboxylate.

5. The flame-retardant yarns and fabrics of claim 1 wherein the fibers of the polyester resin are present in an amount of from about 20 to about 80 percent by weight and the cellulosic fibers are present in an amount of from about 80 to about 20 percent by weight.

6. The flame-retardant yarns and fabrics of claim 1 wherein the flame-retardant cellulosic fibers are cotton.

7. The flame-retardant yarns and fabrics of claim 1 wherein the flame-retardant cellulosic fibers are cellulose acetate.

8. The flameretardant yarns and fabrics of claim I wherein the flame-retardant cellulosic fibers are regenerated cellulose.

9. The flame-retardant yarns and fabrics of claim 8 wherein the regenerated cellulose fibers have dispersed therein a flame-retardant amount of a water-insoluble, liquid phosphonitrilate polymer having the general formula wherein R and R are the same or different alkyl or alkenyl radicals having from 1 to 6 carbon atoms and n is an integer of at least 3.

10. The flame-retardant yarns and fabrics of claim 1 wherein the fibers of the polyester resin also contain an organic bromine or chlorine compound which contains at least 40 weight percent of the halogen in an amount sufficient to provide at least 5 up to about 25 percent halogen, based on the weight of the polyester resin.

UNITED STATES PATENT OFFICE QHICATE 6F QORRECTIGN Q Patent No. 3,866,405 Dated February 18, 1975 Inventofls) William N. Knooka It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: Col. 3, line 43, "6 m l, 5 n 0" should read 6- m l,

5 n O-. Col, 4, line 18, change "gylcol" to read --glycol-;

line 19, delete "glycol"; line 65 the formula should read -HO-(CI-l OH-. Q 301.10, line 5 first column, "No. should read -Sample No.; delete "Sample before "3 second test"; line 65, "of" should read for--. (201.11, line 26, "spitophosphate" should read spirophosphateline 25, delete "spirophosphate". Q

Signed and gealcd this second Day Of September 1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer ('mnmissivnvr uflarenrs and Trademarks 

1. FLAME-RETARDANT YARNS AND FABRICS OF A COMBINATION OF (1) FIBERS OF A SATURATED POLYESTER RESIN OF AT LEAST 75 MOL PERCENT ETHYLENE-2,6-NAPHTHALENE DICARBOXYLATE UNITS AND UP TO 25 SPIROPHOSPHATE MOL PERCENT OF OTHER ESTER UNITS AND AN ARYL SPITOPHOSPHATE OF THE FORMULA
 2. The flame-retardant yarns and fabrics of claim 1 wherein R1 and R2 are both phenyl radicals and the spirophosphate is mixed with the polyester resin in an amount ranging from about 5 to about 25 percent, based on the combined weight of the polyester resin and spirophosphate.
 3. The flame-retardant yarns and fabrics of claim 1 wherein R1 and R2 are both mono-, di- or tri-bromo-substituted phenyl radicals.
 4. The flame-retardant yarns and fabrics of claim 1 wherein the polyester resin is the homopolymer of ethylene-2,6-naphthalene dicarboxylate.
 5. The flame-retardant yarns and fabrics of claim 1 wherein the fibers of the polyester resin are present in an amount of from about 20 to about 80 percent by weight and the cellulosic fibers are present in an amount of from about 80 to about 20 percent by weight.
 6. The flame-retardant yarns and fabrics of claim 1 wherein the flame-retardant cellulosic fibers are cotton.
 7. The flame-retardant yarns and fabrics of claim 1 wherein the flame-retardant cellulosic fibers are cellulose acetate.
 8. The flame-retardant yarns and fabrics of claim 1 wherein the flame-retardant cellulosic fibers are regenerated cellulose.
 9. The flame-retardant yarns and fabrics of claim 8 wherein the regenerated cellulose fibers have dispersed therein a flame-retardant amount of a water-insoluble, liquid phosphonitrilate polymer having the general formula
 10. The flame-retardant yarns and fabrics of claim 1 wherein the fibers of the polyester resin also contain an organic bromine or chlorine compound which contains at least 40 weight percent of the halogen in an amount sufficient to provide at least 5 up to about 25 percent halogen, based on the weight of the polyester resin. 